The present invention relates to apparatus for releasably holding portions of tools or the like, and more particularly to improvements in chucks and analogous apparatus for releasably holding the shanks of rotary parts, such as for releasably securing the shank of a boring or drilling tool to a rotary drill spindle or an analogous rotary member.
It is already known to releasably secure the shank of a rotary tool to a spindle or another driven rotary member by providing or connecting the rotary member with a sleeve-like portion having a conical internal surface and by inserting the shank of the tool into the axial passage of a clamping device having radially movable prongs with conical external surfaces which are complementary to and slidable along the internal surface of the sleevelike portion. If the clamping device is moved axially in one direction, the prongs are caused to move radially inwardly and to clamp the shank to thus establish a torque transmitting connection between the rotary member and the tool. As a rule, the clamping device is moved in the one direction by hand, e.g., by rotating a nut which mates with the enclosure for the clamping device, or by effecting axial movements of pull rods which extend rearwardly of the shank and can be moved axially in the region of the rotary member. The pull rods must be installed in an axial bore of the rotary member which presents many problems, especially if the rotary member is a drill spindle which should transmit torque to a deep well drilling tool. This will be readily appreciated by bearing in mind that a drill spindle is further supposed to provide one or more paths for the flow of lubricating and/or cooling media to and from the locus of penetration of the working end of the tool into the material to be provided with a bore. If the pull rods are installed in the interior of the drill spindle, the dimensions of the latter must be increased or its strength must be reduced if the bore or bores of such rotary member are to provide room for the pull rods as well as for the flow of cooling and/or lubricating media.